let arr = ['a','b','c','d','e']
/* arr.forEach((item,index,arr)=>{
    //console.log(item,index,arr);
    arr[index]=item+'1'
}) */
Array.prototype.my_forEach=function(fs){
    for(let i=0;i<this.length;i++){
    fs(this[i],i,this)
    }
}

arr.my_forEach((item,index,arr)=>{
    console.log(item);
})

